This invention relates in general to vehicle electric power steering assemblies and in particular to monitoring an electric motor in such a vehicle electric power steering assembly.
An electric power steering (EPS) assembly for turning steerable wheels of a vehicle includes a ball nut for transmitting force between an axially movable rack member and an electric motor. Upon actuation of the motor, the ball nut is driven to rotate relative to the rack member and the rotational force of the ball nut is transmitted to the rack member by balls that drive the rack member axially. The axial movement of the rack member by the balls effects turning movement of the steerable wheels.
The EPS assembly uses an active sensor to detect a position of the electric motor. For example, the active sensor may be a Hall effect sensor or a giant magnetoresistance (GMR) sensor. The active sensor may be set to detect the position of the motor at regular intervals—i.e., the active sensor may be strobed to monitor the motor non-continuously—to reduce an otherwise continuous electrical power draw of the active sensor. However, even when strobed, the active sensor still monitors the position of the electric motor when the motor is not turning. The active sensor monitoring the position of the electric motor when the motor is not turning results in unnecessary electrical power consumption. Thus, it would be desirable to activate the active sensor when the motor is turning to monitor a position of the motor.